Whatsapp automation (workflow with trigger and without library fb)

Hi, I'm Tony
I love marketing automation
I help my customers who have ecommerce to automate their marketing actions with email, sms, advertising online!!!
I use active campaign, zapier and hubSpot as crm!
I would also like to automate whatsapp messages on various customer segments, without buying paid libraries to send automated messages on whatsapp
for example ... when a user buys on my ecommerce site, I would like to automatically send a thank you mail as well as a thank you whatsapp message
or nurturing messages
or an automatic message to all customers who have not accessed my site for more than 2 months...
can you help me?
To Give me agvice?
thank you!